Framework: WP_Block: Use reflected type hint for render_callback

[aduth]

Closes #21797
Previously: #21467

This pull request seeks to revise the implementation of block context. As of #21467, the function signature of render_callback was revised in such a way that was intended to be backward-compatible, but which was not always the case in more advanced usage. With the changes proposed in this pull request, a block implementation must explicitly opt-in to receive the full block instance as the argument of render_callback. This should be much more durable than the previous implementation, as existing implementations should not be affected at all, since they would in-fact be passed the same value (an array of attributes), not a value intending to simulate the same behavior (a class implementing ArrayAccess).

From the block implementer's perspective, the developer can opt to receive the block instance by merely providing WP_Block as a type declaration on the first parameter:

register_block_type( 'my-plugin/example', [
    'render_callback' => function( WP_Block $block ) {
        return 'The block name is: ' . $block->name;
    },
] );

Existing use as an array is not impacted:

register_block_type( 'my-plugin/example', [
    'render_callback' => function( $block_attributes ) {
        return 'Has attribute? ' . array_key_exists( 'test', $block_attributes ) ? 'Yes' : 'No';
    },
] );

(Notably, the second code example does not work on the current master branch)

Internally, the implementation uses function reflection to determine whether the render callback is expecting to receive the instance of the block, or the default associative array of block attributes.

Testing Instructions:

Repeat testing instructions from #21467. Optionally, it was made easier to test in later development of #21467, using the "Gutenberg Test Block Context" plugin included in the default development environment, via the associated "Test Context Provider" block.

[github-actions]

Size Change: +23 B (0%)

Total Size: 845 kB

Filename	Size	Change
build/block-library/index.js	112 kB	+23 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
build/a11y/index.js	1.02 kB	0 B
build/annotations/index.js	3.62 kB	0 B
build/api-fetch/index.js	4.08 kB	0 B
build/autop/index.js	2.82 kB	0 B
build/blob/index.js	620 B	0 B
build/block-directory/index.js	6.24 kB	0 B
build/block-directory/style-rtl.css	760 B	0 B
build/block-directory/style.css	761 B	0 B
build/block-editor/index.js	105 kB	0 B
build/block-editor/style-rtl.css	10.1 kB	0 B
build/block-editor/style.css	10.1 kB	0 B
build/block-library/editor-rtl.css	7.13 kB	0 B
build/block-library/editor.css	7.13 kB	0 B
build/block-library/style-rtl.css	7.19 kB	0 B
build/block-library/style.css	7.19 kB	0 B
build/block-library/theme-rtl.css	683 B	0 B
build/block-library/theme.css	685 B	0 B
build/block-serialization-default-parser/index.js	1.88 kB	0 B
build/block-serialization-spec-parser/index.js	3.1 kB	0 B
build/blocks/index.js	57.7 kB	0 B
build/components/index.js	198 kB	0 B
build/components/style-rtl.css	16.9 kB	0 B
build/components/style.css	16.9 kB	0 B
build/compose/index.js	6.66 kB	0 B
build/core-data/index.js	11.4 kB	0 B
build/data-controls/index.js	1.25 kB	0 B
build/data/index.js	8.43 kB	0 B
build/date/index.js	5.47 kB	0 B
build/deprecated/index.js	772 B	0 B
build/dom-ready/index.js	569 B	0 B
build/dom/index.js	3.1 kB	0 B
build/edit-navigation/index.js	3.54 kB	0 B
build/edit-navigation/style-rtl.css	485 B	0 B
build/edit-navigation/style.css	485 B	0 B
build/edit-post/index.js	28.2 kB	0 B
build/edit-post/style-rtl.css	12.5 kB	0 B
build/edit-post/style.css	12.5 kB	0 B
build/edit-site/index.js	10.8 kB	0 B
build/edit-site/style-rtl.css	5.25 kB	0 B
build/edit-site/style.css	5.24 kB	0 B
build/edit-widgets/index.js	8.33 kB	0 B
build/edit-widgets/style-rtl.css	5 kB	0 B
build/edit-widgets/style.css	5 kB	0 B
build/editor/editor-styles-rtl.css	428 B	0 B
build/editor/editor-styles.css	431 B	0 B
build/editor/index.js	43.3 kB	0 B
build/editor/style-rtl.css	3.27 kB	0 B
build/editor/style.css	3.27 kB	0 B
build/element/index.js	4.65 kB	0 B
build/escape-html/index.js	733 B	0 B
build/format-library/index.js	7.32 kB	0 B
build/format-library/style-rtl.css	502 B	0 B
build/format-library/style.css	502 B	0 B
build/hooks/index.js	2.13 kB	0 B
build/html-entities/index.js	622 B	0 B
build/i18n/index.js	3.56 kB	0 B
build/is-shallow-equal/index.js	711 B	0 B
build/keyboard-shortcuts/index.js	2.51 kB	0 B
build/keycodes/index.js	1.94 kB	0 B
build/list-reusable-blocks/index.js	3.12 kB	0 B
build/list-reusable-blocks/style-rtl.css	226 B	0 B
build/list-reusable-blocks/style.css	226 B	0 B
build/media-utils/index.js	5.29 kB	0 B
build/notices/index.js	1.79 kB	0 B
build/nux/index.js	3.4 kB	0 B
build/nux/style-rtl.css	616 B	0 B
build/nux/style.css	613 B	0 B
build/plugins/index.js	2.67 kB	0 B
build/primitives/index.js	1.49 kB	0 B
build/priority-queue/index.js	789 B	0 B
build/redux-routine/index.js	2.84 kB	0 B
build/rich-text/index.js	14.8 kB	0 B
build/server-side-render/index.js	2.67 kB	0 B
build/shortcode/index.js	1.7 kB	0 B
build/token-list/index.js	1.28 kB	0 B
build/url/index.js	4.02 kB	0 B
build/viewport/index.js	1.84 kB	0 B
build/warning/index.js	1.14 kB	0 B
build/wordcount/index.js	1.17 kB	0 B

_{compressed-size-action}

[aduth]

Closing in favor of #21925.